U.S. patent application number 11/997255 was filed with the patent office on 2008-09-11 for electromechanical brake.
Invention is credited to Dietmar Baumann, Chi-Thuan Cao, Bertram Foitzik, Hans Frick, Bernd Goetzelmann, Andreas Henke, Dirk Hofmann, Willi Nagel, Herbert Vollert.
Application Number | 20080217121 11/997255 |
Document ID | / |
Family ID | 36808781 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080217121 |
Kind Code |
A1 |
Cao; Chi-Thuan ; et
al. |
September 11, 2008 |
Electromechanical Brake
Abstract
The invention relates to an electromechanical disk brake which
has a switchable freewheel in order to be configured as a parking
brake. The switchable freewheel includes a clamping roller
freewheel having rollers for locking a motor shaft of an electric
motor of the brake. A locating bearing of the motor shaft of an
electric motor, and the freewheel are accommodated on a cover of a
housing of the electric motor, and all the electric connections of
the disc brake are routed via the cover. The number of components
used can be reduced considerably by the integrated design.
Moreover, the positional tolerances of the freewheel in relation to
the motor shaft can be reduced with the aid of the invention.
Inventors: |
Cao; Chi-Thuan;
(Korntal-Muenchingen, DE) ; Baumann; Dietmar;
(Hemmingen, DE) ; Hofmann; Dirk; (Stuttgart,
DE) ; Vollert; Herbert; (Vaihingen/Enz, DE) ;
Nagel; Willi; (Remseck/Hochdorf, DE) ; Henke;
Andreas; (Diemelstadt, DE) ; Foitzik; Bertram;
(Ilsfeld, DE) ; Goetzelmann; Bernd; (Sindelfingen,
DE) ; Frick; Hans; (Wiggensbach, DE) |
Correspondence
Address: |
RONALD E. GREIGG;GREIGG & GREIGG P.L.L.C.
1423 POWHATAN STREET, UNIT ONE
ALEXANDRIA
VA
22314
US
|
Family ID: |
36808781 |
Appl. No.: |
11/997255 |
Filed: |
June 6, 2006 |
PCT Filed: |
June 6, 2006 |
PCT NO: |
PCT/EP2006/062910 |
371 Date: |
January 29, 2008 |
Current U.S.
Class: |
188/157 |
Current CPC
Class: |
F16D 65/18 20130101;
B60T 13/741 20130101; F16D 2127/085 20130101; F16D 2123/00
20130101; F16D 2127/08 20130101; F16D 2121/24 20130101; F16D
2125/34 20130101; F16D 2127/06 20130101; F16D 2127/10 20130101 |
Class at
Publication: |
188/157 |
International
Class: |
F16D 65/34 20060101
F16D065/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2005 |
DE |
102005035607.9 |
Claims
1-7. (canceled)
8. An electromechanical brake comprising: an electric motor having
a motor shaft; a rotation/translation converting transmission
connected to the electric motor in a manner so as to actuate the
brake; a housing accommodating the electric motor therein; a cover
attached to the housing at one end; a switchable freewheel
connected to the motor shaft in a manner such that in an engaged
position the freewheel locks with respect to the motor shaft to
prevent the motor shaft of the electric motor from rotating in a
direction of releasing the brake, wherein the cover comprises a
bearing plate for the motor shaft of the electric motor and wherein
the cover accommodates the freewheel.
9. The electromechanical brake as recited in claim 8, wherein the
cover comprises a bearing ring for a bearing of the motor
shaft.
10. The electromechanical brake as recited in claim 8, wherein at
least a part of a bearing ring of a bearing of the motor shaft is
an integral component of the motor shaft and wherein said part of
the bearing ring fixes the motor shaft in an axial direction.
11. The electromechanical brake as recited in claim 8, wherein the
cover is part of a locking mechanism of the freewheel.
12. The electromechanical brake as recited in claim 8, wherein the
cover contains all of the electrical connections of the electric
motor and of the freewheel.
13. The electromechanical brake as recited in claim 8, wherein the
brake is a disc brake and the housing is part of a brake caliper of
the brake.
14. The electromechanical brake as recited in claim 8, wherein the
cover comprises a housing for the freewheel.
Description
PRIOR ART
[0001] The invention relates to an electromechanical brake as
generically defined by the preamble to claim 1, which is provided
in particular as a vehicle brake for a motor vehicle.
[0002] Brakes of this kind are intrinsically known. In order to
actuate them, i.e. in order to press a friction brake lining
against a rotatable brake body to be braked, the brakes have an
electromechanical actuating device equipped with an electric motor
and a rotation/translation converting transmission via which the
electric motor is able to press the friction brake lining against
the brake body. Often, a reduction gear train is connected between
the electric motor and the rotation/translation converting
transmission.) It is customary for the rotation/translation
converting transmission to be a screw mechanism, but other
mechanisms--for example a rack-and-pinion drive or a cam that the
electric motor is able to pivot via the reduction gear train,
causing it to press the friction brake lining against the brake
body--can also be used to convert the rotating drive motion of the
electric motor into a translating movement in order to press the
friction brake lining against the brake body. It is also
conceivable to use an electromagnet in lieu of the electric motor.
In the case of a disc brake, the brake body is a brake disc; in the
case of a drum brake, it is a brake drum.
[0003] One example of an electromechanical brake of this kind is
disclosed in DE 102 55 192 A1. To modify it into an auxiliary brake
(parking brake), the knowl brake is equipped with a switchable
freewheel, which in the engaged position, locks a motor shaft of
the electric motor to prevent it from rotating in a releasing
direction of the brake. The locking can occur directly on the motor
shaft or indirectly, for example on a transmission shaft. In an
actuation or application direction of the brake, the motor shaft is
able to rotate freely even when the freewheel is engaged, thus
allowing the brake to be actuated but not released. When the
freewheel is disengaged, the motor shaft is able to rotate in both
rotation directions it is thus possible to apply and release the
brake like a service brake. In the known brake, the freewheel is
coaxially flange-mounted to a housing that accommodates the
electric motor and the rotation/translation converting
transmission.
EXPLANATION AND ADVANTAGES OF THE INVENTION
[0004] The brake according to the invention, with the defining
characteristics of claim 1, has a housing that accommodates the
electric motor. The housing can also accommodate an optional
reduction gear train and/or the rotation/translation converting
transmission. A cover is attached to the end of the housing and,
according to the invention, constitutes a bearing plate with a
bearing for the motor shaft of the electric motor. The freewheel of
the brake according to the invention is also accommodated on or in
the cover. This integrated design of the cover of the housing for
the electric motor reduces the number of individual components and
simultaneously reduces the assembly costs of the brake according to
the invention. The positional accuracy of the freewheel in relation
to the motor shaft is increased since the bearing for the motor
shaft is situated in the cover on which or in which the freewheel
is also accommodated. It is possible to maintain a high degree of
precision of the axial position of the motor shaft in relation to
the freewheel. The high degree of axial precision is important in
order to assure a reliable switching of the freewheel and avoid an
unintended switching of the freewheel. The invention also assures
an exact maintenance of an installation angle of the freewheel, The
invention enables a compact embodiment of the brake.
[0005] The brake according to the invention can be equipped with a
self-amplifying device, which converts a friction force exerted by
the rotating brake body against the friction brake lining pressed
against it during braking into a compressive force that presses the
friction brake lining against the brake body in addition to a
compressive force exerted by the actuating device, thus increasing
the braking force. Examples of possible mechanical self-amplifying
devices include wedge or ramp mechanisms or lever mechanisms. Other
self-amplifying devices, for example hydraulic ones, are also
conceivable.
[0006] The electromechanical brake according to the invention can
be a disc brake, a drum brake, or another brake design.
[0007] Advantageous embodiments and modifications of the invention
disclosed in claim 1 are the subject of the dependent claims.
DRAWINGS
[0008] The invention will be explained in greater detail below in
conjunction with an exemplary embodiment shown in the drawings.
[0009] FIG. 1 is a sectional depiction of an electromechanical
brake according to the invention; and
[0010] FIG. 2 is a cross section through a cover of a housing of
the brake from FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0011] The brake according to the invention, which is shown in the
drawing and labeled as a whole with the reference numeral 1 is a
disc brake. It has an electromechanical actuating device 2 equipped
with an electric motor 3, a multi-stage gear train and reduction
gear train that will be explained below, and a rack-and-pinion
drive or other rotation translation converting transmission. The
electric motor 3, the reduction gear train, and the
rotation/translation converting transmission constitute an
electromechanical actuating device of the brake 1. The electric
motor 3 has a stator 5 with stator windings 6 and a rotor 7 on a
motor shaft 8. The electric motor 3 is an electronically commutated
direct-current motor (brushless BLDC motor), but the invention does
not absolutely require it to be. The electric motor 3 is
accommodated in a housing 9 into which the stator 5 is press-fitted
or fixed in some other way. The motor shaft 8 is supported in the
housing 9 in rotary fashion at one end by a movable bearing 10,
i.e. with axial play. In the exemplary embodiment depicted and
described here, a roller bearing is used as the movable bearing
10.
[0012] At the other end, the housing 9 is closed by a cover 11 that
is manufactured, for example, out of steel or a material of
comparable strength. The cover 11 constitutes a bearing plate of a
fixed bearing 12 of the electric motor 3. In the exemplary
embodiment of the invention depicted and described here, the fixed
bearing 12 is embodied in the form of a ball bearing with balls 13
that are secured in rotary fashion in a ball cage 14. A
circumferential groove with a circular cross section that is ground
into an axial through opening in the cover 11 constitutes an outer
bearing ring 15 of the fixed bearing 12. An inner bearing ring of
the fixed bearing 12 is split in a plane radial to the motor shaft
8: one half of the inner bearing ring is comprised of a bearing
surface 16 with a circular cross section that is ground into an
annular step on the motor shaft 8. A second bearing surface 17,
also with a circular cross section, is embodied on a nut 18 that is
screwed onto the motor shaft 8. The bearing surface 16 of the motor
shaft 8 and the bearing surface 17 of the nut 18 combine to form a
circumferential groove with a circular cross section and constitute
the inner bearing ring 16, 17 of the fixed bearing 12. A bearing
play can be adjusted by rotating the nut 18 on the motor shaft 8;
for example, the nut 18 is secured against rotation on the motor
shaft 8 by a screw-locking varnish.
[0013] In lieu of the above-described bearing construction of the
fixed bearing 12, the rotary support of the motor shaft 8 in the
cover 11 constituting the bearing plate can also be embodied in
other ways. For example, a roller bearing can be press-fitted onto
the motor shaft 8 and inserted into an annular step in the axial
hole in the cover 11 and can be secured there with a retaining ring
(not shown).
[0014] A pinion 19 that is rotationally secured to the motor shaft
8 and is manufactured, for example, by means of grinding, meshes
with a large gear 20, which is supported in a rotationally secured
fashion on a first transmission shaft 21. The transmission shaft 21
can be followed by other transmission stages and a brake-applying
mechanism for a wheel brake, which mechanism can be actuated in any
fashion.
[0015] The housing 9 in which the electric motor 3 is accommodated
is part of a not otherwise shown brake caliper of the brake 1,
which is embodied in the form of a disc brake. The housing 9 can
also be attached to the brake caliper. The housing 9 accommodates
not only the electric motor 3, but also the entire actuating
device, including the brake-applying mechanism. The brake caliper,
of which only a fraction is depicted, namely the housing 9, is
embodied in an intrinsically known fashion as a floating caliper,
i.e. it is guided so that it is able to move transversely in
relation to a brake disc that is not shown. As a result, when one
friction brake pad is pressed against one side of the brake disc, a
second friction brake pad situated on the other side of the brake
disc in the brake caliper is pressed in an intrinsically known
fashion against the other side of the brake disc so that the brake
disc is braked on both sides.
[0016] As is clear from FIG. 2, a switchable freewheel 31 is
accommodated on or in the cover 11. The freewheel 31 is embodied in
the form of a clamping roller freewheel with rollers 32 serving as
the clamping or locking elements. Other designs of the freewheel 31
are also possible. The rollers 32 are situated distributed around
the motor shaft 8 of the electric motor 3. They are accommodated in
recesses of a roller cage 33 that is situated in an annular
intermediate space between the motor shaft 8 and the cover 11.
Spring elements 34, which are likewise situated in the recesses of
the roller cage 33, act on the rollers 32 in the circumference
direction so that the rollers 32 are lifted away from the motor
shaft 8. The rollers 32 roll in pockets 35 in the axial bore of the
cover 11. In this case, a bottom surface of the pockets 35
constitutes a bearing surface for the rollers 32. The bottom
surfaces of the pockets 35 constituting the bearing surfaces extend
in spiral fashion in relation to the motor shaft 8. Through
rotation of the roller cage 33 around the motor shaft 8, the
rollers 32 of the freewheel 31 roll in the pockets 35 and move in
spiral fashion toward the motor shaft 8. If the rollers 32 are
resting against the pockets 35 and against the motor shaft 8, then
the spiral course of the pockets causes the rollers 32 to prevent
the motor shaft 8 from rotating in one rotation direction. This
rotation direction is a releasing direction of the brake 1. The
motor shaft 8 is, however, able to rotate in the applying
direction. The above-described rotated position of the roller cage
33 is the engaged, locked position of the freewheel 31 in which the
freewheel 31 locks to prevent a rotation of the motor shaft 8 in
the releasing direction, but permits an actuation of the brake
1.
[0017] If the roller cage 33 is rotated back into its starting
position and the spring elements 34 lift the rollers 32 away from
the motor shaft 8, then the freewheel 31 is disengaged and the
motor shaft 8 can rotate freely in both rotation directions.
[0018] In order to rotate the roller cage 33 and therefore to
engage the freewheel 31, the freewheel 31 is equipped with an
electromagnet 36, which has a winding 37 and an armature 38. A
housing 39 of the electromagnet 36 is integrally joined to the
cover 11 of the housing 9 of the electric motor 3. A cover 40 that
closes the housing 39 of the electromagnet 36 constitutes a yoke of
the electromagnet 36, which closes the magnetic flux path. The
electromagnet 36 switches the freewheel 31 by means of a tappet 41
that is situated tangential to the roller cage 33 of the freewheel
31. The tappet 41 engages a cam 42 that protrudes radially outward
from the roller cage 33; the opposite side of this cam is acted on
by a spring element 43 in the form of a helical compression spring,
which is accommodated in a pocket in the cover 11, outside of the
roller cage 33, and is supported in the cover 11. When current is
supplied to the coil 37 of the electromagnet 36, this exerts
traction on the armature 38 and, via the tappet 41, pushes against
the cam 42 of the roller cage 33 of the freewheel 31. This rotates
the roller cage 33 into the engaged position as described above. In
the engaged position of the freewheel 31, the brake 1 can be
applied further, but cannot be released. If the brake 1 is actuated
while the freewheel 31 is engaged, a mechanical stress builds up,
which keeps the rollers 32 of the freewheel 31 clamped between the
motor shaft 8 and the cover 11 even if the electromagnet 36 is no
longer supplied with current. The brake 1 is therefore kept in the
actuated position even when it is without current and can thus be
used as an auxiliary brake. In order to release the actuated brake
1, the electric motor 3 actuates it, which releases the mechanical
prestressing so that the spring element 43 rotates the roller cage
33 of the freewheel 31 back into the disengaged position. The motor
shaft 8 is then able to rotate freely and the brake 1 can be
released and used as a service brake. The cover 11--which is
equipped with the pockets 35 for the rollers 32, cooperates with
the rollers 32 and together with the rollers 32, prevents the motor
shaft 8 from rotating in the releasing direction of the brake 1
when the freewheel 31 is engaged--constitutes part of a locking
mechanism of the freewlheel 31.
[0019] The cover 11 of the housing 9 contains all of the electrical
lines of both the electric motor 3 and the electromagnet 36; the
electrical lines are brought together in one or more electrical
plugs that are not shown in the drawing. This has the advantage of
achieving a simple electrical connection of the electric components
of the brake 1 according to the invention.
* * * * *